...I then am supposed to lead through the already placed pro a la sport climbing then belay my partner up...

This is the truly stupid part of the idea. 1. As you mentioned, what if the gear becomes loose or the 2nd (inexperienced) climber kicks a piece out? 2. As you mentioned, you've never climbed trad and don't have the ability to properly judge a piece. 3. What if you don't see a piece of gear, you'll have a much longer and dangerous run out? 4. Sounds like he's a better climber than you. You may have to "test" placements that he would never fall on. 5. What if you can't get past a section? With a top rope, you can cheat to keep the party together. Better have an escape plan if you can't get past something and don't have the gear to build a mid-pitch anchor. 6. You're going to be stuck waiting while the 4th (inexperienced) climber has to clean.

The idea of leaving trad gear behind to "sport climb" with shouldn't even be done by any climbers. Either the 3rd person places their own protection on lead, or climbers 2-4 top rope it as a single party.

I would question any trip being lead by someone who thinks this is a good idea.

It's doable if your buddy knows his stuff. If you're going to commit to it with four people bring 3 ropes. Make sure you can lead belay and have your buddy with the most experience lead. Top rope the next guy who tags another rope. As guy number two climbs have him unclip the gear from his top rope and clip the tag line. When he gets to the anchor, set up tr with the tag line. Repeat for guy number 3. Have guy number 4 clean the route, ideally the guy with the second most experience. Repeat for 4 pitches. This way everybody unskilled top ropes. Make bomber/equalized 4 piece anchors just to ease the mind of have four people tied in. Be prepared for this to take awhile and have fun.

^^LOL That's what I was thinking. People are so eager to bestow their knowledge that they miss little things like this OP was so long ago, odds are they either said fuck it, or did it and survived. Sorry, your sage opportunity has come and gone.